Annual report pursuant to Section 13 and 15(d)

STOCK-BASED COMPENSATION - Additional Information (Details)

v3.8.0.1
STOCK-BASED COMPENSATION - Additional Information (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares issued during the period (in shares)       72,760,969 72,932,222
Time Lapse Restricted Shares          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Vesting increment, starting with the second anniversary, over six years 20.00%        
Award vesting period 6 years        
Shares issued during the period (in shares) 0 0 700,000    
Common stock reserved for issuance upon exercise of stock options (in shares) 4,300,000        
Unrecognized compensation cost $ 32.9 $ 29.9      
Unrecognized compensation cost, period for recognition 3 years 10 months 24 days 3 years 9 months 18 days